SNOTEL Data Collection Network Fact Sheet

Introduction

The Natural Resources Conservation Service (NRCS) installs, operates,
and maintains an extensive, automated system to collect snowpack and
related climatic data in the Western United States called SNOTEL (for
SNOwpack TELemetry). The system evolved from NRCS's Congressional mandate
in the mid-1930's "to measure snowpack in the mountains of the West
and forecast the water supply." The programs began with manual
measurements of snow courses; since 1980, SNOTEL has reliably and
efficiently collected the data needed to produce water supply forecasts
and to support the resource management activities of NRCS and others.

Climate studies, air and water quality investigations, and resource
management concerns are all served by the modern SNOTEL network. The
high-elevation watershed locations and the broad coverage of the network
provide important data collection opportunities to researchers, water
managers, and emergency managers for natural disasters such as floods.

Meteor Burst Technology

SNOTEL uses meteor burst communications technology to collect and
communicate data in near-real-time. VHF radio signals are reflected at a
steep angle off the ever present band of ionized meteorites existing from
about 50 to 75 miles above the earth. Satellites are not involved; NRCS
operates and control the entire system.

An available map shows the locations of over 730 SNOTEL sites in 11
western states including Alaska. The sites are generally located in remote
high-mountain watersheds where access is often difficult or restricted.
Access for maintenance by NRCS includes various modes from hiking and
skiing to helicopters.

Sites are designed to operate unattended and without maintenance for a
year. They are battery powered with solar cell recharge. The condition of
each site is monitored daily when it reports on 8 operational functions.
Serious problems or deteriorating performance trigger a response from the
NRCS electronic technicians located in 6 Data Collection Offices.

The SNOTEL sites are polled by 2 master stations operated by NRCS in
Boise, Idaho, and Ogden, Utah. A central computer at NRCS's National Water
and Climate Center (NWCC) in Portland, Oregon controls system operations
and receives the data collected by the SNOTEL network.

New SNOTEL System Capabilities

Basic SNOTEL sites have a pressure sensing snow pillow, storage
precipitation gage, and air temperature sensor. However, they can
accommodate 64 channels of data and will accept analog, parallel, or
serial digital sensors. On-site microprocessors provide functions such as
computing daily maximum, minimum, and average temperature information.
Generally, sensor data is recorded every 15 minutes and reported out in a
daily poll of all sites. Special polls are conducted more frequently in
response to specific needs.

The new generation of remote sites, master stations, and central
computer facilities allows for hourly interrogation of remote sites. The
system has the ability to vary the configuration of a remote site by
transmitting the appropriate commands telling the remote site what sensors
to turn on or what parameters to send.

A variety of calculations can be made on any sensor channel. For
example, the user can select maximum, minimum, average, standard
deviation, or circular averaging.

Each sensor can be accessed independently at a specific interval. For
example, wind speed may be sensed every minute during the day to arrive at
an average, while the snow pillow may be accessed every 15 minutes for the
accumulated total.

System performance has increased over the years, mainly due to a better
understanding of meteor burst communication characteristics and improved
equipment.

While a 95 percent response to a system- wide poll is the standard,
over 99 percent is common.

Data Storage, Management and Accessibility

All data are received by the SNOTEL central computer, which in turn is
linked to the Centralized Forecasting System (CFS) in the NWCC where data
can be accessed. Once on CFS, the data are in a relational database, where
various analysis and graphics programs are available. Current and
historical data and analyses are available by dialing in to the CFS, by
disk or tape media, paper copy, or more recently via NWCC homepage and
internet.

While carrying out the agency mission is paramount, NRCS is interested
in supporting the research and operational data collection needs of
others. The current system offers excellent opportunities.

For More Information

For more information, contact the NRCS State Office in any of the
western states or: